Hi Everyone, Been working on a camera using some Navy aerial lenses. Theyre real large heavy ones made by Pacific Optical. Anyway, I've been struggling with a nice, neat, and above all strong focusong rack to move these lenses with. I tried a screw drive with crown gears, but could not get the crown gears to work smoothly enough. I work on large laboratory instruments for a living, and noticed that the cogged belt drives that are used on many of the moving mechanisms, might be just the thing. I just installed one on my project today, and it works great. Fast smooth and precise. On this camera, the lens standard platform slides on 13mm dia stainless rods with linear bearings, so there is very little friction. I may have to add some friction to keep the lens from moving after it is adjusted. In this design, the two cogged pulleys are fixed to the camera frame, and the platform is clamped to the belt. The rear pulley shaft comes out of the side of the frame and has a knob on it. When I turn the knob the belt moves and the lens platform goes with it. It all has to be pretty strong since the lenses weigh 3 to 6 pounds each!
Gene Johnson _______________________________________________ Cameramakers mailing list [EMAIL PROTECTED] http://rmp.opusis.com/mailman/listinfo/cameramakers
